Why is there no color in the scene I exported with vtkVRMLExporter

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I want to export the result, but there is always no correct color after opening it with ParaView. If you have any other suggestions please let me know.

polydata = vtkAppendPolyData()
    reader = vtkNIFTIImageReader()
    reader.SetFileName('Brats18_2013_10_1_seg.nii.gz')

    for label,color,name in zip(labels,Colors,CC):
        pointColors = vtkUnsignedCharArray()
        pointColors.SetNumberOfComponents(3)
        pointColors.SetName('Colors')

        dmc = vtkDiscreteMarchingCubes()
        dmc.SetInputConnection(reader.GetOutputPort())
        dmc.SetValue(0, label)

        smooth = smooth_functions(dmc, 1)

        output = smooth.GetOutput()

        for i in range(output.GetNumberOfPoints()):
            pointColors.InsertNextTuple3(*color)

        output.GetPointData().Update()
        output.GetPointData().SetScalars(pointColors)
        polydata.AddInputData(output)


    mapper = vtkPolyDataMapper()
    mapper.SetInputConnection(polydata.GetOutputPort())
    actor = vtkActor()

    actor.SetMapper(mapper)

    ren = vtkRenderer()
    ren.AddActor(actor)
    renWin = vtkRenderWindow()
    renWin.AddRenderer(ren)
    iren = vtkRenderWindowInteractor()
    iren.SetRenderWindow(renWin)

    iren.Initialize()
    iren.Start()

    exporter = vtkVRMLExporter()
    exporter.SetRenderWindow(renWin)
    exporter.SetActiveRenderer(ren)

    exporter.SetFileName("cylinders11.wrl")
    exporter.Write()

I originally used multiple actors to display different parts, but the exported result cannot be opened by ParaView, so I used vtkAppendPolyData

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On it on StackOverflow : vtk - Why is there no color in the scene I exported with vtkVRMLExporter - Stack Overflow